In peptide synthesis or synthesis of various compounds, some reactions require protection of functional groups such as a carboxy group, a hydroxy group, a diol group, an amino group, an amide group, and a mercapto group. A protecting group for those functional groups is required to be capable of protecting the functional groups by a simple method and being removed from the functional groups under moderate conditions. Benzyl ester (Bn), and tert-butyl ester are known as examples of a protecting group for a carboxy group. According to recent reports (Patent Literatures 1 and 2), benzyl alcohol compounds and diphenylmethane compounds are found to be useful as protecting groups.